Hypersensitivity pneumonitis is an immunologic lung disease caused by chronic inhalation of chemicals or organic dusts. Its chronic stage makes diagnosis more difficult because other interstitial diseases share the same clinical and radiological presentation, usually requiring open lung biopsy to confirm the diagnosis. The authors reviewed the confirmed cases in the last 11 years at the Thoracic Diseases Institute [Instituto de Doenças do Tórax] of the Rio de Janeiro Federal University [UFRJ]. In this period, eight cases were confirmed by histopathological studies. Main symptoms were dyspnea and coughing. All cases showed interstitial infiltrates on radiological studies and restrictive functional patterns were found in 70% of the cases. All seven patients treated with corticosteroids responded with improved clinical symptoms, although some did not have radiological or functional response. Once the diagnosis is established, patients must avoid the causative environment because the disease may progress to fibrosis if exposition continues.

Keywords: Extrinsic allergic alveolitis. Case-control studies. Diagnosis.